1. Field of the Invention
The present disclosure relates to a lightguide used in a vehicle LED headlamp to generate a low beam or a fog beam. The lightguide forms a sharp horizontal cutoff with horizontal spread, and finds application in automotive beam patterns including SAE low beam, SAE\ECE Fog, and other uses. The lightguide provides a main body with a reflective rear edge surface whose arcuate profile determines a horizontal cutoff and an exit lens whose arcuate exit profile determines a horizontal spread of the emitted light beam pattern. Lightguides are used in motor vehicles, but are not limited thereto.
2. Description of the Related Art
In the prior art, a single LED light source was used to make beam patterns with different horizontal cutoffs and horizontal spreads. In low beam and fog pattern applications, in the prior art, LED light sources were used with reflectors, thick lens, and elliptical with projector lens. Internal mirrors, shields or folders were used to form horizontal spreads.
Other lightguides are known in U.S. Pat. No. 7,607,811 (Okada); U.S. Pat. No. 7,661,860 (DeLamberterie); EP 1992868 (Gasquet); EP 1992868 (DeLamberterie); EP 1895228 (Gasquet); U.S. Pat. Appl. Pub 2009/0135621 (Muegge); U.S. Pat. Appl. Pub 2009/0091944 (DeLamberterie); U.S. Pat. Appl. Pub 2006/0285347 (Okada); and U.S. Pat. No. 6,945,672 (Du).
U.S. Pat. Appl. Pub 2009/0091944 (DeLamberterie) discloses various high beam patterns obtained by a planar light source using a curved reflector having a concave parabolic rear reflective surface and providing a vertical light exit aperture through which parallel light rays produced by a light source pass out of the reflector in a collimated manner (FIG. 3). DeLamberterie FIG. 12 discloses a horizontal cutoff being achieved by disposing the light source so that the optical focus of the parabolic rear edge is situated on the rear edge of the light source instead of being situated at the center of the light source. DeLamberterie FIG. 13 discloses an embodiment where the vertical light exit aperture is convex towards the front, in an elliptical profile, and the rear reflective surface has a hyperbolic profile with a convexity turned towards the rear. In this embodiment, a first focus is situated on the light source, and a second focus is merged with a focus of the light exit aperture. The light rays passing out of the reflector are parallel to the optical axis.